Great web page. I can't say that I agree with all of the remarks about controlled carrier modulation.
I used to own a T-60 and it did great. A good old DX-60 sound great sometimes. Same way - very little idling carrier power, but tons of modulation power. Those little rigs make 30 watts of AM sound like 100 watts. OK they may not have a BAND-BLANKING carrier like some of the 300-400 watt plate mod rigs out there, but when adjusted properly they can be very intelligible on the air and if you use a D-104 or such on them, often give very pleasant sounding audio, in my estimation. Just some food for thought. I wouldn't mind having a T-60 or DX-60B with a digital VFO and drive one of my Thuderbolts with it in AM linear mode. Bet I'd be heard better than with a 30 watt plate mod rig all by itself (grin!) On 30 Sep 2002 at 22:00, John E. Coleman wrote: > Hi George: > You have obviously done you homework. And I agree that in the > majority of cases 1-2 dbs won't make a lot of difference. The main > reason for the article is that there is a ceiling, and how we might > make the most of it. The ceiling could be a linear amplifier with a > 800 watt ceiling. The same circumstances would apply if that is what > a man has to work with. The legal ceiling is different than it was, > not just because of the problem of power reduction but in the fact > that it is a hard ceiling not soft as it was in the old days. One KW > DC input limit could easily be a rectangular wave modulated micro wave > with a PEP of 10KW and still be legal. > > All I'm saying is that with a ceiling, either legal or > equipment, that there may be better ways to operate with less > distortion and bandwidth while improving the level of reception at the > same time. > > I must admit that it was the legal limit that prompted me to > write the article since it's a little bit of a cramp in my style to be > forced to turn the variac down to 220 watts input to the final for a > carrier output of 165 watts. Because my voice is so asymmetrical I > must reduce the carrier to this low level in order to stay with in the > 1500 watt PEP limit. So the next time I get on 75 mtrs I'll have a > switch that will flip the microphone phase and increase the voltage on > the final at the same time. Then I'll get reports on this for about a > month and see what every one says. I'll try to keep good records and > post the results. > > It's all in the fun of experimentation as for as I'm concerned. > Heck, I've seen a 4-6 DB gain just by putting 20 dollars into some > material to get the antenna up a little higher and that leads me to a > subject that is very interesting to all I'm sure. I'll always use > open wire feeds if it is at all possible. > > Good luck, > John, WA5BXO > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of George Pritchard > Sent: Monday, September 30, 2002 7:30 AM To: [email protected] > Subject: RE: [AMRadio] New link to Info on AM and legal power limits. > > Would anyone consider using the transmission line loss of 1dB as the > "output power of the transmitter" into the antenna? That would mean > 475 watts carrier for symmetrical sinewave instead of the "understood" > 375 limit. Just more fuel for the fire. Just have a power sensor at > the antenna input terminal. Claim it's the final output of the > station. Consider this: 1KW DC input. Transmitter is 70% eff at TEN > METERS. 700 Watts out into the 1dB transmission line. That gets power > down to 550 Watts carrier into the antenna which is .87 dB over the > "spec" if considering symmetrical modulation. If one were to drop the > audio gain by .87 dB, the station is in compliance with the 1500 Watts > at the ANTENNA input terminal. Its all "fly doodoo" in the ocean as > far as I'm concerned. I the end... most people see the potential 3000 > Watts PEP (750 watts X4)old limit versus the 1500 Watt new limit as > the 3 dB cut in power. Maybe, but it is only 1/2 S-unit using the > worst case math loss. I include my PATH loss in the math loss to > justify using my homebrew rig. Actually, the new rules give the SSB > operators at least 300 watt more PEP. 2000 X 60% class B = 1200 watts > old rules. My opinion is that there was no intention to reduce power, > since it really didn't for the MAJORITY of the hams. Only a > "convenient global" power measurement method was needed. The AMers > (myself include) brought attention to the AM power issue). Maybe it > was (and is) un-necessary. Lets not forget that the "DC input rule" > change was also for SSB guys as well. Since the SSB manufacturers were > not burdened to include both Plate voltage and Plate current on their > linears (or rigs), The FCC did not want to dig into the final's > circuitry to make the frivolous and dangerous measurement. These are > the words (paraphrased) by Steven mendohlson, director of the Hudson > division during those power struggle days. I think you are all loosing > to much sleep over this... Just forget about it, use your rigs in a > polite manner, operate and be happy. Nobody cares about a few dB > anyway. 10 dB! yes of course. 1 to 3dB? be real. Most meters are 1dB > best accuracy anyway. George AB2KC > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of John E. Coleman > Sent: Sunday, September 29, 2002 11:32 PM To: AMRadio Subject: > [AMRadio] New link to Info on AM and legal power limits. > > > I've be working on a document that might be of interest to many folks. > With the help of K4KVY, WA3WDR, W5TOB and a month or two of night work > I've come up with something good I hope. Anyway here it is. > > http://www.qsl.net/wa5bxo/asyam/aam3.html > > I hope it is of some use to someone and encourages experimentation. > > John, WA5BXO > > > > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio > > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
